Part of Option H

1. Option H: Further Human Physiology IB Biology

2. H1 - Hormonal Control Hormones = chemical messengers secreted by endocrine glands into the blood and transported to specific target cells. Example: insulin – produced by pancreas; target: liver cells Hormones can be: Steroids: progesterone, estrogen, testosterone Peptide derivative: insulin; leptin (appetite control-metabolism regulation / target = hypothalamus) Tyrosine derivatives: thyroxine (thyroid hormone) = regulates metabolism

3. Hormone Absorption Different hormones = difference in solubility Steroid hormones = can cross plasma membrane/nuclear membrane – bind with receptor, affecting gene expression directly Protein hormones = cannot cross the membrane = trigger a cascade reaction mediated my chemicals called second messengers. Ex: adrenalin = attaches to membrane receptor = stimulates transformation from glycogen to glucose

4. Hypothalamus/Pituitary - Hypothalamus:Links nervous and endocrine systems(Pituitary: double lobed gland below hypothalamus) Hypothalamus controls each lobe differently: Hypothalamus neurons produce hormones that are transported and stored in vesicles in the axon located in the posterior pituitary. Nerve impulses cause the release of the vesicles into blood stream. Hypothalamus also produces GnRH (gonadotropin releasing hormone) = transported to anterior pituitary by portal vein = GnRH stimulates production of FSH (follicle stimulating hormone) and LH (luteinizing hormone) by anterior pituitary (target tissue)

6. Integration between pituitary and hypothalamus:ADH hypothalamus neurosecretory cells produce ADH (anti-diuretic hormone or vasopressin = promotes osmoregulation) ADH is transported through nerve impulses by to the posterior pituitary where it is stored Osmoregulatory sensitive cells in the hypothalamus sense changes in solute concentration ADH is released from its storage region and secreted into the blood target tissue = collecting ducts of kidney = makes it more permeable to H20 = the body reabsorbs more H20, diluting blood solutes = OSMOREGULATION

7. H2 - Digestion Digestive juices are secreted into the alimentary canal (lumen of gut) by GLANDS. Exocrine Glands + juice content: salivary glands = saliva: amylase, lipase, mucus, slightly alkaline solution that moistens the food, gastric glands in stomach wall = gastric juice: pepsin, hydrochloric acid, salt, water, mucus pancreas = pancreatic juice: amylases, trypsin, chymotrypsin, lipase, carboxipeptidase, bicarbonate ion small intestine = enteric juice: carbohydrases, dipeptidases, enterokinases (enteropeptidases)

8. Pancreas – An exocrine and endocrine gland

9. Exocrine Glands release secretion into ducts which open onto cavities like skin, mouth, alimentary canal acini (acinus = singular – “berry”) = cluster of secretory cells 2 portions: glandular + duct Exocrine cells have: rough endoplasmic reticulum (b) well developed next to nucleus (c) and Golgi apparatus (d), more secretory vesicles with protein, more mitochondria (a)

12. Cellulose humans lack cellulase cellulose remains undigested/released in feces cows/sheep = symbiotic relationship with cellulose digesting bacteria (termites/protozoan too) cellulose = fiber = creates bulk (mass) = stimulates peristalsis/satiety

13. Digestive Enzymes Pepsin/Trypsin = proteases Pepsinogen (stomach) + Trypsinogen (pancreas) = zymogens = inactive enzyme precursor chemically altered after secretion to become active (this prevents self digestion of the cell)

14. Ulcers/Cancer in the stomach acidic environment = barrier to infections mucus protects stomach wall Helicobacter pylori (bacterium) cause stomach infection leading to ulcers -> can lead to cancer Lipid Digestion Lipase – water soluble enzyme – acts on water-insoluble lipids (tend to coalesce into larger droplets) = PROBLEM Triglycerides turn into fatty acids and glycerol Bile acts as “detergent” = breaks fat into tiny droplets (emulsion), increasing surface area exposed to lipase

15. H3 - Absorption of Digested Food Structure of ileum: villi = fingerlike projections that increase surface area of small intestine crypts = contain secretory cells of intestinal secretion mucosa = mucus secreting membrane muscles = create contractions – promote movement of chyme along alimentary canal serosa = tough outer membrane composed of collagen Unabsorbed material / eliminated with feces (egested) = cellulose, lignin, bile pigments, bacteria and intestinal cells

17. Absorption in the small intestine absorption happens through epithelial cells covering each villus nutrients must cross epithelial cells (not enough space to go between cells = tight junctions) cell membrane = microvilli = increase surface area even more cell uses ATP to make endocytosis happen (cell needs many mitochondria for that) Transport in the intestine can involve: Simple diffusion (molecules follow concentration gradient, crossing the membrane through channel proteins – “pore”) Facilitated diffusion (ex. Fructose) Active transport (ex. Glucose = pumps use energy to move nutrient against concentration gradient) Endocytosis (pynocytosis = cells uses energy = vesicles carry substances)

18. Absorption of fatty acids monoglycerides, bile salts, fatty acids = combine forming micelles -> diffuse across membrane -> inside cell they reassemble into triglycerides protein is added to lipid -> vesicles called chylomicrons exocytosis -> release lipoprotein from cell -> enter lacteals vessels (lymphatic system) -> converge into lymph vessels that carry them to circulatory system